I have recently upgraded my rear and side surrounds to Polk LSIFx and LCi in ceiling speakers. This means I now have 7 channels of 4ohm speakers. Before, I had 8 ohm Polks for my rear and side surrounds. I notice now that when I watch very dynamic movie scenes such as explosions or car chases etc. that there is considerable amount of distortion coming from my speakers at a volume of -15 to -25 db.(and louder) This is a new phenomenon and it had not even occurred to me that it could be clipping with an amp like the 770 but......?? I am not even sure what clipping sounds like but it has been suggested to me that this is it.